Long pipes used in well drilling utilize threaded ends, external or internal, for connection to other pipes or pipe couplings. The pipe lengths may vary. Since the pipes are fed into deep holes, sometimes hundreds of feet into the ground, it is important that the joints be reliably secure and as tight as possible. A defective joint may require the pulling of a long string of pipes which is expensive and time consumming. It will be understood that while the present invention is described in connection with long pipe lengths, it may be adapted to pipes, tubes, bar stock and other long work units.
With lower level production, the end threading of the work units can be accomplished reasonably well with a stationary threading means and some device for holding the work while being threaded. If the threading is accomplished by turning the work, this can create a problem since the long work elements are not always straight and the turning of the element will cause it to whip at the free end. The result can be an imperfectly threaded element.
With the increased demand and production of long length pipe resulting, to a degree, from increased oil well exploration and drilling, there has arisen a need for a means of threading pipe in larger quantities, and of improving the quality. The low lot threading equipment is not adequate to meet the demand.
Thus, it is an object of the present invention to provide a system and apparatus for machining and threading the ends of long work units in a production sequence which insures accuracy as well as being adapted to relatively large output. It is a further object to provide an apparatus which adapts to work units which are not absolutely straight throughout their lengths or which are not perfectly round at the end of be machined. It is another object to perform multiple machining and threading operations in sequence on elongate work units. The words "pipe", "work unit", "work element" or "stock" are applied to the particular workpiece being handled.